Global navigation satellite systems (GNSS) are broadly defined to include GPS (U.S.), Galileo (proposed), GLONASS (Russia), Beidou (China), IRNSS (India, proposed), QZSS (Japan, proposed) and other current and future positioning technologies using signals from satellites, with or without augmentation from terrestrial sources. Information from GNSS is being increasingly used for computing a user's positional information (e.g., a location, a speed, a direction of travel, etc.).
In GNSS, multiple satellites may be present, with each transmitting a satellite signal. A received signal at a GNSS receiver contains one or more of the transmitted satellite signals. To obtain the information from the respective transmitted signals, the GNSS receiver performs a signal acquisition/tracking procedure. More specifically, the GNSS receiver searches for the corresponding transmitted satellite signals in the received signal and then locks onto them for subsequent tracking of the corresponding satellites to receive the satellite information.
When a GNSS receiver is first turned on, it searches for satellite signals that match known PN (pseudorandom noise) codes. A match of a known PN code and a doppler frequency with a received signal identifies the transmitting satellite. With multiple satellites present in GNSS systems and the length of the PN codes is long, the dimensions of the search space increases the acquisition time spent in acquiring the signal. Fast signal acquisition plays an important role in achieving faster position determination. With the increase in demand for satellite-based positioning, fast signal acquisition will be a limiting factor for achieving lower latencies in determination of user's position and speed.